The current invention relates to electrically operated toothbrushes in which the rotary motion of an electric motor is converted to oscillating motion of the toothbrush head along the axis of the brush handle by multiple means including a helical groove in one part of the toothbrush which guides a cam follower in another part of the toothbrush.
Different approaches to movable toothbrush heads are to be found in the prior art. U.S. Pat. No. 4,783,869 discloses a manual toothbrush head mounted on a reciprocating and oscillating shaft. Motion is imported to the head by the user's brushing movements. More particularly, as the user brushes his/her teeth right-to-left, the toothbrush head automatically moves up and down on his/her teeth. This translation of movement is achieved through a web-shaped groove cut into an internal part of the toothbrush handle that mates with a projection on a movable shaft attached to the toothbrush head (FIGS. 3–6). As the shaft moves left and right, the interaction of groove and projection translates that movement into up-and-down movement of the toothbrush head.
U.S. Pat. No. 6,347,425 B1 describes another approach to imparting movement to a toothbrush head in which rotational movement of a motor is translated into reciprocating side-to-side and rocking up-and-down motion of a toothbrush head. This translation of movement is achieved by an offset in a powered shaft which interacts with a groove in a floating head (FIGS. 3–4).
Another apparatus for imparting movement to a toothbrush head is disclosed in U.S. Pat. No. 6,371,294B1 issued Apr. 16, 2002. In this patent, power is transmitted from a motor to the head through a series of gears. Rotational (FIG. 4) or oscillating (FIG. 12) motion is imparted to the head.